In hermetically enclosed refrigerant compressors, as known from, for example, domestic refrigerators or freezers or air-conditioning systems, it is endeavoured to achieve a small component height in order to obtain a large effective space for the cooling. One way of keeping the height of the compressor small is to use a drive motor with an external rotor, as a drive motor with an external rotor has a smaller component height as a drive motor with an internal rotor and the same performance.
A rotor with the features mentioned in the introduction is, for example, known from FR 2 734 958 A1. Here, the permanent magnets are arranged on the inside of the cylinder ring, and are tightened against each other in the circumferential direction by means of holdfasts, which engage the cylinder ring.
However, it takes a substantial effort to build such a rotor into a motor, as a very careful handling is required.
Another possibility of fixing permanent magnets in an external rotor involves the insertion of permanent magnets in pockets, which are arranged in the rotor. Such a solution is, for example, known from EP 1 536 543 A1.
Further, there is a possibility of gluing the permanent magnets onto the cylinder ring. Such a solution is, for example, known from US 2006/0076845 A1.
However, the use of adhesives is not unproblematic. Also providing a plastic housing with pockets, into which the permanent magnets are inserted, involves a substantial effort.